Armari XCP

Verdict: The XCP is the first true piece of PC art.

As with the launch of a new sports car, the first question that generally comes to mind when a new PC arrives in the CPC lab is 'how fast is it?' This query can be answered by a plethora of benchmarks, with the results given in frames per second, points or perhaps even teraflops if you're that way inclined. Armari, the winner of the 2005 Dream PC Labs test, seems to have taken a different view and designed a PC that wows you for what it is, rather than the components inside it or the numbers it generates. It's more than the maths.

Aside from its dominating presence, the most striking aspect of the XCP is the immersion of the motherboard, CPU, RAM and expansion cards in a transparent liquid. The idea behind this design is that rather than using a combination of fans and waterblocks (plus all the associated tubes, pumps, radiators and reservoirs) to cool the components by pumping liquid over the motherboard, all these components can be cooled in one fell swoop.

However, as even readers with only an elementary grasp of physics will know, you can't simply pour water over an electrical circuit, as the results would be catastrophic. Instead of water, Armari has used Fluorinert, one of the few genuinely non-electrically conductive liquids available. Fluorinert is widely used to cool supercomputer and military electronic circuits, as it has excellent thermodynamic properties. The downsides to Fluorinert are that it's very expensive (more than £200 a litre), much denser than water and evaporates into the atmosphere at room temperature.

Armari has solved the evaporation problem by placing the motherboard in a sealed chamber. To accommodate any type of PC, the chamber has been designed to be large enough to house an E-ATX motherboard. However, simply filling it with Fluorinert wouldn't be enough to keep the PC cool for more than a few minutes. The challenge, therefore, was to figure out a way for the XCP to transport the Fluorinert around the main chamber to conduct heat from the components, then remove the coolant, cool it down and recirculate it back to the main chamber.

On paper, this didn't seem like much of a problem, but the XCP's three-year gestation period should provide some idea of the engineering challenges Armari faced. For starters, Fluorinert has a nasty tendency to expand and contract as it heats and cools, so the entire system had to be pressure-sealed, as standard water-cooling radiators and rubber tubes would crack. Instead, Armari has used 1/2in metal tubes lined with Teflon, which are specified to withstand up to 2,000psi of pressure so that they won't crack when the pressure changes. There are also four emergency pressure release valves in the roof of the tank.

Cooling the liquid

The next challenge was to work out a way to remove heat from the Fluorinert. This stage of the cooling process involved incorporating a traditional water-cooling loop and linking it with the Fluorinert loop via a huge heat exchanger, which is situated in the base of the case under the main chamber. The heat from the Fluorinert is transferred into the water/ethylene glycol mixture in the traditional water-cooling loop, and then exhausted via two mammoth triple 120mm-fan radiators positioned on either side of the base. The six fans mounted on these radiators are the only fans in the system, and are temperature-controlled by two Koolance controllers, so they rev up and down depending on which components are installed in the main chamber. If that isn't enough to keep the components cool, an external 1HP water-chiller can be plugged in, which is sufficiently powerful to reduce the temperature of the water-cooling loop by 20ûC, and the temperature of the Fluorinert by 10ûC.

As Fluorinert is so much denser than water, a regular PC water-cooling pump isn't strong enough to move it around. Instead, the XCP employs a giant, AC-powered custom-built Laing 115W pump. This is situated in the base of the PC and accounts for a good deal of the system's very high power draw. Once the Fluorinert has been cooled by the heat exchanger, it's then pumped into the main chamber through a massive hole under the motherboard. To aid the cooling process, Fluorinert is also pumped into the chamber through a bank of jets in the silver bars you can see running along the front and rear edges of the motherboard.

As the main chamber containing the motherboard and expansion cards is full to the brim with Fluorinert, it has to be sealed to prevent the coolant leaking and evaporating, or being contaminated by foreign objects such as dust. For obvious reasons, this makes plugging in all the cables that a modern PC needs a nightmare. To overcome this problem, Armari spent a lot of money designing and manufacturing its own custom PCB and cables - one end of which is submerged in Fluorinert, while the other end is hard-wired into the base. A second set of cables then transmits the information from the first set of cables into panels on the front and rear of the base, allowing you plug in USB 2 devices, audio jacks and a DVI screen. This proved much harder than simply using USB 2 and FireWire extension cables, as found in most cases, because Armari had to locate the pin-out of each connector and replicate it. Multiplying this process by the number of cables (more than 40 for motherboard power alone) gives some idea of the scale of the problem.

However, while it's one thing to design and manufacture such a technically impressive system, Armari also wanted to make sure the XCP was visually distinctive too. Using the Cray-2 supercomputer for inspiration, Armari decided that the only thing better than a liquid-immersed PC was a PC with a waterfall. To achieve the waterfall effect, Armari designed two side tanks into which the heated Fluorinert flows via two small slits near the top of the main chamber. The side tanks are filled approximately an inch high, which means that as the Fluorinert leaves the main chamber it cascades down in a waterfall into each of the side tanks. The effect is completed by a bank of coloured LEDs that shine through the waterfalls, and can be programmed with a handy remote control to cycle through a random pattern of colours or display a single colour. On a purely practical level, the waterfalls are superfluous to the operation of the XCP, but they're integral as they embody the XCP's 'submerged-in-liquid' design. It's a work of art, and just one example of what makes the XCP a true Dream PC.

A sense of scale

As you can see from the photos, the level of engineering required to control the flow of Fluorinert, then cool and recycle it, means that the XCP is one of the biggest PCs ever built. Part of the problem was the sheer quantity of Fluorinert required to submerge an entire PC - close to 40 litres. This necessitated designing an incredibly heavy, 15mm-thick aluminium plate to provide structural integrity between the base and the three tanks above. The tanks are constructed from a combination of 15mm and 22mm acrylic sheets, cut and shaped by Carville, a company that also makes acrylic components for the defence and medical industries. These sheets are chemically bonded using an optically clear process that makes it almost impossible to see the join unless you study it very closely. As a result of all these parts, the XCP tips the scales at around 80kg, while filling it with Fluorinert adds another 70kg. Armari has fitted two carry handles to either side, but even so, it's impossible to move the XCP while it's full of Fluorinert. It's also imperative that it sits on an extremely strong desk.

Elements such as this demonstrate the Herculean efforts Armari has gone to in sourcing the best suppliers and components from around the world to help design and manufacture the XCP. Coupled with the three-year design process, and the six months it took to build the first prototype, the entire project has cost Armari close to £100,000. This isn't how much it would now cost to build an XCP, however, so Armari found it hard to tell us the price for which XCPs would sell - which is why we can't actually review the XCP. As there are literally hundreds of custom-made components inside the XCP, Armari would need a minimum order of around ten to 20 units to consider putting it into production, and even then it would take several months to build each unit. However, the company estimated that it could produce an XCP for around £11,750 (including 40 litres of Fluorinert) if these conditions were met. Of course, this is a huge amount to spend on a PC, but then you're not buying any old PC - the XCP is truly unique, and unmatched by anything any other company has to offer.

The components

Compared with the immersion cooling system and waterfalls, the rest of the XCP is very conventional. Armari has integrated a single 5.25in drive bay in the base for an optical drive, plus three removable 3.5in drive bays for S-ATA II hard disks. The entire system is powered by a 1.5kW Thermaltake Toughpower PSU, but there are two bays for additional 750W 12V PSUs if your system has particularly power-hungry components.

Armari has built only one complete XCP so far, and because the company was showing it at an Intel event after collecting it from Custom PC, Armari fitted a Skulltrail motherboard, two ATI Radeon HD 4870 X2 graphics cards running together in CrossFire and 8GB of FBDIMM memory. Although contact with the Fluorinert wouldn't damage the electric fan motors, the fans had to be removed from the motherboard, CPU and graphics cards. This is because Fluorinert is so much denser than air or water, so it would cause the fan motors to burn out and die after just a few days.

Each of the quad-core Core 2 Extreme QX9775 CPUs has been overclocked from 3.2GHz to 4GHz, but due to stability problems with the early ATI graphics driver, we were unable to benchmark the XCP fully. The only benchmark we could reliably run was Cinebench R10, which returned a groundbreaking score of 29,011 - a stunning 34 per cent faster than the Scan 3XS Great White PC. However, far more impressive than this stupidly fast benchmark number was the sight of the Fluorinert roiling due to the heat coming off the components as the system was put under load. The graphics cards and system RAM in particular emit huge amounts of heat into the Fluorinert, causing turbulence as the heat rises to the top of the main chamber. This effect was so eye-catching that we kept finding other members of staff gazing at it, entranced by the heated Fluorinert twisting and turning above the graphics cards.

Unlike most PCs, however, which are simply enclosures for a particular set of components that quickly become outdated, the XCP isn't tied to a single set of components. The lid of the main chamber is sealed by more than 20 bolts, but it can easily be removed, so the motherboard and accompanying components can be replaced. A three-way valve controls the flow of Fluorinert from the main pump, so if you want to change a component, you simply configure the valve to empty the main chamber by pumping the coolant into the two side tanks.

Believe it or not, Armari plans to develop the XCP further. A second prototype is already in the works, and this will use a combination of Fluorinert immersion cooling with LN2 (liquid nitrogen) cooling for the CPUs. This is currently at the design stage, but Armari is considering the possibility of using an LN2 generator (at the moment, this is used to cool the electronics in electron microscopes), which extracts nitrogen from the atmosphere, so you don't need to buy a supply of LN2 every few weeks.

Conclusion

Although the standard of systems submitted to our annual Dream PC Labs test has steadily risen over the years as the best and brightest of the PC industry struggle to outdo one another, the Armari XCP must rank as a premier example of how to build a truly stunning PC. The immersion of a PC in liquid caused quite a few gasps of shock and awe from people passing through the Custom PC lab - it defies belief, even when you know the liquid is Fluorinert, not water. Admittedly, the XCP isn't the first liquid-immersed computer in history, but it's the first and only liquid-immersed PC (Cray 2 and Cray 932's notwithstanding) built to a commercial standard.

What's more, the XCP wasn't developed by an international mega-corporation such as HP or Dell - it was conceived by a small UK-based company that won the Dream PC Labs test way back in 2005. Here's hoping Armari and its obviously bonkers staff continue to impress and inspire us.